Fuel tank with air tank under bed in 49

[jocww]

So now that I got my bed on, i need to figure out where to put the gas tank and air tank. My air tank is from ride tech and is the 5 gallon size. The gas tank I dont have. I am looking at this one from ebay https://www.ebay.com/itm/15-Gallon-T...9aPiFi&vxp=mtr its only 120 bucks. Where else can I put these, I would prefer not to have any in the cab or bed if possible.

The first 2 pics of where I tried it today, but I think I would like it farther in the back in the last pic where my uncle and my dad were looking at it.
Any suggestions or opinons are appreciated.